The present invention concerns a device and method for relieving vasospasm affecting the intracranial arteries. More particularly the present invention concerns a device and method of performing non-balloon angioplasty within tiny arteries so as to relieve intracranial vasospasm.
The arterial make up of the head, and more specifically of the brain, includes important routes that are, of necessity, small and tortuous in character. As such, intracranial brain artery networks are comprised of vessels having small diameters and almost “hairpin”-like turns.
Patients with ruptured brain aneurysms, known as subarachnoid hemorrhage (or SAH) can develop intracranial vasospasm as a delayed complication. In vasospasm, the arteries supplying the brain are narrowed as a result of constriction and/or thickening of the blood vessel wall. Because the narrowed vessel lumen restricts blood flow, lack of blood supply to the brain distally can result in a stroke.
Current management of vasospasm utilizes a combination of mechanical dilatation (angioplasty) and pharmacological intervention of the spastic vessels. Mechanical angioplasty is commonly performed with a microcatheter with a small balloon attached at its end. Balloon angioplasty is widely accepted to be a safe, effective and durable treatment for vasospasm, but it is limited in that the balloon microcatheters are by design larger diameter and stiffer than simple microcatheters. As such, these microcatheters usually cannot be steered into vessels that are smaller or more tortuous. In addition, these balloons are chosen based on the diameter when maximally inflated and it is difficult to inflate a balloon to a diameter less than its designed maximum. For these reasons, angioplasty of affected arteries is usually reserved for larger, proximal vessels, while smaller, more tortuous, more distal vessels are not mechanically treated.
At present, most angioplasty of arteries affected by intracranial vasospasm is performed with specialized low-radial-pressure, compliant balloon microcatheters, such as the Sentry, manufactured by Target/Boston Scientific and the Equinox, manufactured by MicroTherapeutics, Inc. However, even these specialized balloon microcatheters have not overcome all of the noted shortcomings in that the tip profile and stiffness of these devices still prevents them from being steered into small, tortuous vessels. Moreover, the balloons tend to inflate in an all-or-nothing manner, making it less desirable to, for example, use a 3.5 mm diameter balloon to dilate a vessel with a 2.5 mm normal diameter due to the potential risk of over dilatation.
In rare occurrences, some individual practitioners have performed angioplasty of small, tortuous, distal arteries simply by passing a microcatheter (without a balloon) through the vessel. However, this technique is often not helpful because currently available microcatheters have generally blunt tips and in general have too small an outer diameter to accomplish much angioplasty.
Chemical or pharmacological intervention is also practiced. For example, the affected arteries can be infused with vasodilating drugs, to facilitate opening of the arteries. Infusion can be carried out by direct infusion through use of a catheter or by placement of such chemicals on, for example, an angioplasty balloon such that the chemical is placed onto the affected area of the arteries. However, there are inherent limitations in that the bathing of tissue with dilating chemicals, while effective, is generally effective for only the short period while the chemical is present or is present in an effective amount.